Probe cards have been used for testing semiconductor integrated circuits formed on wafers on the wafer level. As described in Japanese Kokai Patent Application No. 2006-041333, a probe card has plural vertical probe pins and MLC/MLO or other base plates for multilayer relays.
FIG. 16 is a schematic cross-sectional view illustrating a cantilever-type probe card in the prior art. As shown in the figure, the probe card has probe card base plate 10 and resin 14 with which plural probes 12 are attached on the probe card. Said resin 14 is fixed on probe card base plate 10. The probes fixed by a resin or the like form a so-called pin row, and plural pin rows may be set to form a two-dimensional configuration. Usually, 1-3 pin rows are set. FIG. 17(a) is a schematic diagram illustrating the configuration of a 3-row pin configuration. It includes first row of probes 12-1, second row of probes 12-2, and third row of probes 12-3.
In the prior art, in order to lower the electrical resistance between the probes and bump electrodes, the probes are overdriven so that the tip portions of the probes slide on the bump electrodes to remove the natural oxide film or other resistance components on the surface of the bump electrodes, and guarantee a sufficient contact area. As shown in FIG. 17(a), for the cantilever-type probes, the probes are first positioned with respect to bump electrodes 18 of wafer 16. Then, as shown in FIG. 17(b), probes 12-1, 12-2, 12-3 of the 3-row pins are overdriven, that is, they are further pressed from the state when they are in contact with bump electrodes 18.
FIG. 18 is a diagram illustrating the state of displacement of the probes when said cantilever-type probes are overdriven. The overdriven probes have their tips displaced around supporting point 20. In the figure, δ represents the overdrive distance (deflection), F represents the pin pressure (contact pressure), Sc represents the scrub distance (sliding distance), D represents the diameter of the wire (diameter of the probe pin), L represents the free end length (installing length), l represents the tip length, and θ represents the incident angle (attaching angle).
Assume that the probes are made of ReW; the pin diameter is 200 μm; the beam length is 3,500 μm; the tip diameter is 80 μm; and the overdrive is 60 μm. Table 1 lists the relationships among the length from the bending portion of each row to the tip (tip length), pin pressure F, and sliding distance Sc.
TABLE 1Tip lengthPin pressure FSliding distance ScFirst row250 μm5.6 g12.4 μmSecond row450 μm5.6 g18.0 μmThird row650 μm5.8 g23.2 μm
Here, one should note the sliding distance Sc of each row when the overdrive is applied. Because different rows have different tip lengths of the probes, different rows have significantly different values of distance Sc.
When the contact object is a bonding pad, gold bump, lead solder bump or other material with relatively low hardness, even if pin pressure F of the probe is not very high, the contact resistance still can be effectively suppressed. However, for a lead-free bump electrode or other contact object with high hardness, a high pin pressure F is required. When overdrive is applied such that prescribed pin pressure F is met for all of the probes, as explained above, because different rows have different values of sliding distance Sc, for certain probes (such as those of the third row), the sliding distance Sc may become excessive. Because sliding distance Sc becomes a probe trace on the bump electrode, a probe trace over the tolerable range leads to deterioration of the bump electrode, and deterioration in the appearance of the bump electrode. Also, depending on the probe, when sliding distance Sc increases, the quantity of metal cut off by the tip of the probe increases, the quantity of debris of the bump deposited on the tip of the probe increases, and the cleaning frequency of the probe increases. As a result, the lifetime of the probe decreases. As a result, it is necessary to ensure that the difference in the sliding distance between different rows is small.
As one scheme to address the aforementioned problem, the probe may be made of BeCu (beryllium copper) with a relatively low hardness so as to reduce the difference in the sliding distance, that is, probe trace, between different rows. However, in this method, the probes themselves wear out, so that the lifetime of the probes decreases, and this is undesirable.
As another scheme to address the aforementioned problem, a vertical-type probe card represented by the cobra-type shown in FIG. 19(a) and FIG. 19(b) may be used. For a cobra-type vertical probe card, the end portions of probes 30 are fixed by resin 32 and the probe tips are aligned. When the probe tips are brought in contact with metal bump 18, as shown in FIG. 19(b), as overdrive is applied, bending portion 34 of each of probes 30 elastically deforms. Because the various probes have the same shape, even when the probes are overdriven, the pin pressure and sliding distance are the same for the various probes. As a result, it is possible to suppress the probe traces on bump electrodes 18 to within a prescribed range.
Consequently, with a cobra-type vertical probe card, the problem associated with a cantilever-type probe card probing a bump electrode made of a lead-free material is not present. However, when a device with a low number of probes (such as about 54 pins) is manufactured, as noted in Table 2, compared with the cantilever-type, the initial cost of a cobra-type vertical probe card is very high. As a result, a cobra-type vertical probe card is inappropriate for small-quantity multi-type manufacturing.
TABLE 2Cantilever-typeVertical typeCleaning frequency20100[Contact/Clean]Lifetime of probe4503500[K Contact]Initial cost3401000[¥1,000]Operating cost1100370[¥]